Electric utility subsidiary - Consolidating statement of income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Operating expenses
Purchased power	$ 136,000	$ 165,000
Total expenses	568,356	694,535
Operating income	69,506	89,214
Other income (loss)
Allowance for equity funds used during construction	1,413	1,609
Interest and other charges
Allowance for borrowed funds used during construction	499	614
Income taxes	19,979	25,721
Net income	32,339	46,260
Preferred stock dividends of subsidiaries	473	473
Net income for common stock	31,866	45,787
Hawaiian Electric Company
Condensed Income Statements, Captions [Line Items]
Revenues	399,741	512,455
Operating expenses
Fuel oil	118,403	203,547
Purchased power	103,250	123,969
Other operation and maintenance	70,084	58,515
Depreciation	29,389	27,301
Taxes, other than income taxes	38,201	48,184
Total expenses	359,327	461,516
Operating income	40,414	50,939
Other income (loss)
Allowance for equity funds used during construction	1,123	1,472
Equity in earnings of subsidiaries	7,692	8,917
Interest expense and other charges, net	(11,238)	(10,487)
Interest and other charges
Allowance for borrowed funds used during construction	388	559
Income before income taxes	38,379	51,400
Income taxes	11,235	15,710
Net income	27,144	35,690
Net income attributable to Hawaiian Electric	27,144	35,690
Preferred stock dividends of Hawaiian Electric	270	270
Net income for common stock	26,874	35,420
HELCO
Condensed Income Statements, Captions [Line Items]
Revenues	88,055	104,931
Operating expenses
Fuel oil	23,385	31,500
Purchased power	21,893	29,491
Other operation and maintenance	16,399	14,047
Depreciation	9,313	8,975
Taxes, other than income taxes	8,384	9,763
Total expenses	79,374	93,776
Operating income	8,681	11,155
Other income (loss)
Allowance for equity funds used during construction	145	65
Interest expense and other charges, net	(2,680)	(2,748)
Interest and other charges
Allowance for borrowed funds used during construction	53	25
Income before income taxes	6,199	8,497
Income taxes	2,277	3,202
Net income	3,922	5,295
Preferred stock dividends of subsidiaries	134	134
Net income attributable to Hawaiian Electric	3,788	5,161
Net income for common stock	3,788	5,161
Maui Electric
Condensed Income Statements, Captions [Line Items]
Revenues	85,674	102,693
Operating expenses
Fuel oil	35,018	51,253
Purchased power	10,864	11,456
Other operation and maintenance	17,519	16,044
Depreciation	5,541	5,327
Taxes, other than income taxes	8,163	10,024
Total expenses	77,105	94,104
Operating income	8,569	8,589
Other income (loss)
Allowance for equity funds used during construction	145	72
Interest expense and other charges, net	(2,435)	(2,505)
Interest and other charges
Allowance for borrowed funds used during construction	58	30
Income before income taxes	6,337	6,186
Income taxes	2,338	2,335
Net income	3,999	3,851
Preferred stock dividends of subsidiaries	95	95
Net income attributable to Hawaiian Electric	3,904	3,756
Net income for common stock	3,904	3,756
Other subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenues	0	0
Operating expenses
Other operation and maintenance	0	0
Total expenses	0	0
Operating income	0	0
Interest and other charges
Income before income taxes	0	0
Income taxes	0	0
Net income	0	0
Net income attributable to Hawaiian Electric	0	0
Net income for common stock	0	0
Consolidating adjustments
Condensed Income Statements, Captions [Line Items]
Revenues	(28)	(17)
Operating expenses
Operating income	(28)	(17)
Other income (loss)
Equity in earnings of subsidiaries	(7,692)	(8,917)
Interest expense and other charges, net	28	17
Interest and other charges
Income before income taxes	(7,692)	(8,917)
Income taxes	0	0
Net income	(7,692)	(8,917)
Net income attributable to Hawaiian Electric	(7,692)	(8,917)
Net income for common stock	(7,692)	(8,917)
HECO Consolidated
Condensed Income Statements, Captions [Line Items]
Revenues	573,442	720,062
Operating expenses
Fuel oil	176,806	286,300
Purchased power	136,007	164,916
Other operation and maintenance	104,002	88,606
Depreciation	44,243	41,603
Taxes, other than income taxes	54,748	67,971
Total expenses	515,806	649,396
Operating income	57,636	70,666
Other income (loss)
Allowance for equity funds used during construction	1,413	1,609
Interest expense and other charges, net	(16,325)	(15,723)
Interest and other charges
Allowance for borrowed funds used during construction	499	614
Income before income taxes	43,223	57,166
Income taxes	15,850	21,247
Net income	27,373	35,919
Preferred stock dividends of subsidiaries	229	229
Net income attributable to Hawaiian Electric	27,144	35,690
Preferred stock dividends of Hawaiian Electric	270	270
Net income for common stock	$ 26,874	$ 35,420